The present invention relates to an antenna for very high and/or ultrahigh frequencies and includes at least one wire-like conductor arranged in a window pane, for example, in a window pane of a motor vehicle provided with a set of parallel heating wires interconnected by two transverse busbars for applying direct current thereto.
Pane antennas of this kind are known, for example, from the German Patent Publication DE 3618452.A1 and DE-OS 3719692.A1. In these known antennas, the heating set or sets on the window pane are utilized for the reception of signals in the range of meter wavelenghts. The antenna terminals are located always on the busbars for applying the direct current to the heating wires and at the point in the proximity to a busbar on the metal frame surrounding the window pane, for example, in the form of a conductive body of a motor vehicle. The prior art antennas make use of the possibility to tap different reception signals at different points of the busbars and of the conductive frame in order to process the mutually different signals in an antenna diversity system. The antenna conductors and the heating conductors in the case of a single pane window are printed on the glass whereas in the case of a compound or laminated window pane the conductors are in the form of thin wires sandwiched between the glass laminae of the compound window pane.
These known antennas have the disadvantage that the power supply network connected of necessity to the busbars on the window pane in order to apply thereto the heating direct current, considerably affects the impedance conditions of the antennas. Therefore, in order to decouple for high frequencies the busbars from the part of the power supply network which supplies the heating direct current, suitable decoupling networks have been used as illustrated for example in FIG. 1 of the DE 3618452 or in FIG. 1 in DE 3719692. In the motor car technology, such decoupling networks have been made of discrete components whose maintenance and storage is expensive.
Moreover, the number of antenna types which can tap reception signals at the busbars for the heating wires is limited due to the difficulties encountered in decoupling such signals. If it is desired to construct several antennas in combination with the set of heating wires, it has been necessary in prior art technology using the tapping of the antenna signals at the busbars to subdivide the heating field into several portions by interrupting the busbars, so that the individual antennas are decoupled one from the other. For many technological and cost-related reasons, the number of subdivisions of the heating array and the number of the requisite decoupling networks is very limited. Therefore it is desirable to utilize the heating array in the window pane as an antenna, nevertheless, the number of antenna terminals at the busbars should be kept as low as possible.
It has been also known to install one or more antennas consisting of one or more interconnected antenna conductors on the part of the window pane, which is not occupied by the heating array whereby the above described antennas are additionally installed in combination with the heating field. Since usually the portion of the motor vehicle window pane which is free of the heating wires is relatively very small, only a very small number of such antennas can be installed and due to the lack of space, only narrow antennas can be employed even if border antenna structures would be desirable.